From: Ferruh Yigit <ferruh.yigit@amd.com>
To: fengchengwen <fengchengwen@huawei.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
Ori Kam <orika@nvidia.com>, Thomas Monjalon <thomas@monjalon.net>
Subject: Re: Question about add ethdev loopback set API
Date: Thu, 15 Dec 2022 17:50:38 +0000 [thread overview]
Message-ID: <9347efde-b15f-a611-affd-a486a47bb44c@amd.com> (raw)
In-Reply-To: <3fa49fba-4eaf-afd4-7677-9a50713eca04@huawei.com>
On 12/15/2022 12:46 PM, fengchengwen wrote:
> On 2022/12/14 18:38, Ferruh Yigit wrote:
>> On 12/14/2022 7:25 AM, fengchengwen wrote:
>>> On 2022/12/13 19:25, Ferruh Yigit wrote:
>>>> On 12/13/2022 10:04 AM, fengchengwen wrote:
>>>>> Hi Ferruh,
>>>>>
>>>>> During the test, we need to delineate where go wrong when encountered
>>>>> e.g. CRC error. In this scenario, loopback is useful.
>>>>>
>>>>> I think we can add a loopback set API which could set inner or outer loop,
>>>>> and user can use telemetry to set the loopback in the above scenario.
>>>>>
>>>>> I'd like to hear your opinion about add a loopback set API.
>>>>>
>>>>
>>>> Hi Chengwen,
>>>>
>>>> Is the intention to test ethdev layer or driver?
>>>>
>>>> It is possible to use ring vdev to create a loopback and to test ethdev
>>>> layer.
>>>>
>>>> For driver, it can be possible to create physical loopback connection,
>>>> or even can implement loopback Rx/Tx burst functions in driver.
>>>> Using another host to send/receive packets to DUT (device under test) is
>>>> another approach.
>>>>
>>>>
>>>> What kind of loopback implementation do you have in your mind?
>>>
>>> Mainly MAC layer and lower physical layer:
>>>
>>> -------- --------------- ------------ ---------- --------------------
>>> | | | - rx | | - rx - | | - rx - | | |
>>> | Host | - | MAC | - | SerDes | - | PHY | ==== | Packet Generator |
>>> | | | - tx | | - tx - | | - tx - | | |
>>> -------- --------------- ------------ ---------- --------------------
>>>
>>> The support loopback in hns3 platform:
>>> Inner loopback subtypes: which host send pkts and recv and then verify:
>>> Serdes tx to rx
>>> PHY tx to rx
>>>
>>> Outer loopback subtypes: which Packet-Generator send pkts and recv and then verify:
>>> MAC tx to rx
>>>
>>> I think we could support the above loopback types, and maybe other PMD platform support
>>> more loopback types.
>>>
>>
>> There is a 'lpbk_mode' field of "struct rte_eth_conf", to configure
>> loopback in 'rte_eth_dev_configure()',
>> but it isn't fine grained to define the possible modes you mentioned
>> above. Currently '0' means loopback disabled and non zero means it is
>> enabled, details left to drivers.
>>
>> 'lpbk_mode' is 32bit, we have space to define detailed loopback modes.
>
> Emm, I found the lpbk_mode is not defined in a unified manner, which is vendor specified.
>
>>
>>
>> Having loopback configuration in 'rte_eth_dev_configure()' requires port
>> to stop and reconfigure to enable/disable loopback.
>> If it is possible to change loopback behavior without full
>> reconfiguration cycle, we can add two new APIs to enable/disable
>> loopback. But this has the downside of two different APIs change same
>> config, and we had problems related this in the past.
>
> Yes, the 'use rte_eth_dev_configure() to config loopback' is inflexible, and I also notice
> the testpmd command "set tx loopback port-id on/off", and it invoke PMD's public API which
> is rte_pmd_ixgbe/i40e/bnxt/dpaa_set_tx_loopback. According to this information, loopback
> needs to be configured during running.
>
> So I suggest add one API:
>
> int rte_eth_dev_set_loopback(uint16_t port_id, uint32_t lpbk_mode), and costraint
> this API can only invoke when port is started, if turn off (lpbk_mode==0) then should
> recovering rte_eth_conf's lpbk_mode.
>
> Also the lpbk_mode is vendor specified.
>
'lpbk_mode' is 32bit, we can define as some X bits still will be used as
vendor specific manner, but rest is defined. I think this can work.
OK to have new API, and use 'lpbk_mode' parameter of it exactly as it is
used by rte_eth_dev_configure().
>>
>>
>>
>> Also there is a hairpin feature in ethdev, that connects Rx queue back
>> to Tx queue, but not sure if that justifies your "MAC tx ro rx" testcase.
>>
>>
>> .
>>
next prev parent reply other threads:[~2022-12-15 17:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-13 10:04 fengchengwen
2022-12-13 11:25 ` Ferruh Yigit
2022-12-14 7:25 ` fengchengwen
2022-12-14 10:38 ` Ferruh Yigit
2022-12-15 12:46 ` fengchengwen
2022-12-15 17:50 ` Ferruh Yigit [this message]
2022-12-16 1:07 ` fengchengwen
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